Control of the linear density of fibres

The error of measurement of the linear density of cord PCA fibre by a standard method of measurement and using a system of the ASKN type was estimated and analyzed. Control of the linear density of a fibre using the ASKN system is more accurate, effective, and informative than the standard method of measurement. Recommendations are made on calibration and testing the ASKN system using simulators and a production control variant using a portable instrument with system functions is proposed. The proposed method of estimating and analyzing errors of measurement can also be used for controlling other properties of PCA fibres and operating conditions, as well as for other types of fibres. __________ Translated from Khimicheskie Volokna, No. 1, pp. 57–60, January–February, 2006.     

Burning-rate response functions of nitramine-based propellants and HMX from microthermocouple data measurements

The results of experimental burning-rate and burning-surface temperature measurements, which were obtained for nitramine-based propellants and HMX at various pressures and initial temperatures, are used to determine the pressure and temperature sensitivities of the burning rate and surface temperature and the criteria of burning stability. It is shown that the one-dimensional and quasistationary approaches are valid. Based on the data obtained, the functions of burning-rate response to acoustic pressure oscillations are calculated. The estimates of calculation errors show that smoothing of the experimental dependences of the burning rates and surface temperatures allows us to obtain response functions with acceptable errors. The influence of the melted layer on the surface of burning HMX on the stability criteria and the response functions of HMX is taken into account. Introduction of HMX into the structure of catalyst-containing ballistite propellants is found to decrease appreciably the response-function amplitudes. The effect of the propellant structures on these functions is studied. Translated fromFizika Goreniya i Vzryva, Vol. 36, No. 1, pp. 12–22, January–February, 2000. This work was partially supported by the Russian Foundation for Fundamental Research (Grant No. 97-03-32076).     

Experimental investigation of agglomeration during combustion of aluminized solid propellants in an acceleration field

Agglomeration during combustion of solid rocket propellants in an acceleration field up to 60 was studied experimental. In the experiments, the acceleration direction and magnitude were varied. The amount, chemical composition, and particle size of the agglomerates and the structure of the surface layer were determined as functions of the acceleration magnitude and direction. The most significant feature of the effect of tensile accelerations is an increase in the agglomerate mass to a certain limiting value, and that of compressive accelerations is the formation of a layer of condensed products on the burning-propellant surface. The data obtained provide a deeper understanding of the general physical picture of agglomerate formation and aluminized-propellant combustion and highlight the range of engine operation problems under flight conditions due to the presence of condensed combustion products. __________ Translated from Fizika Goreniya i Vzryva, Vol. 45, No. 1, pp. 38–46, January–February, 2009.     

Burning of Nano-Aluminized Composite Rocket Propellants

Several aluminum nanopowders were examined and compared with the final goal to evaluate their application in solid rocket propulsion. A detailed investigation of pre-burning properties by the Brunauer-Emmet-Teller method, electron microscopy, X-ray diffraction, and X-ray photoelectron spectroscopy was carried out. Ballistic properties and the combustion mechanism of several aluminized propellant formulations were investigated. In particular, aggregation and agglomeration of metal particles at and near the burning surface were analyzed by high-speed high-resolution color digital video recordings. All tested nano-powders are of Russian production; their physical characterization was carried out at the Istituto Donegani (Novara, Italy); ballistic studies were performed at the Solid Propulsion Laboratory (Milano, Italy) using laboratory and, for comparison, industrial composite propellants based on ammonium perchlorate as an oxidizer. Results obtained under a fair variety of operating conditions typical of rocket propulsion indicate, for increasing nano-Al mass fraction or decreasing nano-Al size, larger steady burning rates with essentially the same pressure sensitivity. While aggregation and agglomeration phenomena still occur, their significance may be reduced by using nano-Al instead of micro-Al. __________ Translated from Fizika Goreniya i Vzryva, Vol. 41, No. 6, pp. 80–94, November–December, 2005.     

Surface layer dynamics in the pyrolysis of ammonium perchlorate-hydrocarbon binder propellants

Mixtures of ammonium perchlorate particles and polybutadiene binder appear to exhibit preferential accumulation of one or the other component on the pyrolyzing surface over a range of rocket-operating pressures. At low pressures, the surface layer is enriched with the oxidizer, and at high pressures, it is enriched with the binder. The degree of accumulation of the oxidizer is found to be higher for smaller particle size. These experimental data can be explained by the difference in activation energies for pyrolysis of the oxidizer and the binder. The particle size effect is explained by consideration of nearly identical surface temperatures for the oxidizer and binder in mixtures with fine particles, but different temperatures for those with coarse particles. The results obtained are important to the explanation of the mechanism of plateau burning rate exhibited by certain composite propellants. Translated fromFizika Goreniya i Vzryva, Vol. 36, No. 5, pp. 57–62, September–October, 2000.     

Method of measuring the modulus of elasticity of carbon tow

In comparison to static and ultrasound methods, the examined method of measuring the modulus of elasticity of carbon fibres (tow) has the following advantages: the method of measurement is contactless and nondestructive; the minimum necessary linear size of the tow required for the measurement (5 cm) is much less than for other existing methods; the results of the measurement are not a function of the method of fastening and tension of the tow; continuous monitoring of the elastic properties during movement of the tow is possible; the E of the tow in both elastic and in the initial fibre material can be measured; this allows measuring the modulus of elasticity of fragments of structures manufactured with fibre materials. __________ Translated from Khimicheskie Volokna, No. 1, pp. 57–59, January–February, 2007.     

Methodical problems of solid-propellant burning-rate measurements using microwaves

A brief review of microwave techniques for measuring solid-propellant burning rate is given, and the principles of the techniques are described. A burning-rate meter operating in the 2-mm microwave band, which was designed by the authors, is described, and tentative results obtained using this device are reported. Limitations of the method, sources of errors, and problems related to the choice of the microwave band and measurement systems are discussed. Problems that should be solved to increase the accuracy and reliability of burning-rate measurements using microwave techniques are considered. Translated fromFizika Goreniya i Vzryva, Vol. 36, No. 1, pp. 68–78, January–February, 2000. This work was supported by Brigham Young (USA, project leader Prof. M. Beckstead) and the Federal program “Integration” (Grant No. 1080K).     

Electrical effects in propellant compositions radiated by electrons

Radiation-induced electrical conductivity of composite and ballistite solid propellants under pulsed (2.5 · 10⁻⁶ sec) and continuous (1–100 sec) radiation by a flux of fast electrons is studied. Conditions for the development of an electrical breakdown during electron radiation are determined, and the relation between this phenomenon and the composition of the composite propellant is considered. For the ballistite propellant, radiation-induced conductivity is studied both in the highly elastic and in the vitreous state. Based on experimental results, the parameters of a semi-empirical model of radiation-induced conductivity are determined for both types of propellants. __________ Translated from Fizika Goreniya i Vzryva, Vol. 43, No. 5, pp. 52–63, September–October, 2007.     

Condensed combustion products of aluminized propellants. IV. Effect of the nature of nitramines on aluminum agglomeration and combustion efficiency

The condensed combustion products of two model propellants consisting of ammonium perchlorate, aluminum, nitramine, and an energetic binder were studied by a sampling method. One of the propellants contained HMX with a particle size D ₁₀ ≈ 490 μm, and the other RDX with a particle size _{D 10} ≈ 380 μm. The particle-size distribution and the content of metallic aluminum in particles of condensed combustion products with a particle size of 1.2 μm to the maximum particle size in the pressure range of 0.1–6.5 MPa were determined with variation in the particle quenching distance from the burning surface to 100 mm. For agglomerates, dependences of the incompleteness of aluminum combustion on the residence time in the propellant flame were obtained. The RDX-based propellant is characterized by more severe agglomeration than the HMX-based propellant — the agglomerate size and mass are larger and the aluminum burnout proceeds more slowly. The ratio of the mass of the oxide accumulated on the agglomerates to the total mass of the oxide formed is determined. The agglomerate size is shown to be the main physical factor that governs the accumulation of the oxide on the burning agglomerate. __________ Translated from Fizika Goreniya i Vzryva, Vol. 42, No. 4, pp. 78–92, July–August, 2006.     

Some aspects of the effect of the porosity of the condensed phase on the combustion of nitrocellulose propellants

This paper considers the mechanisms involved in the effect of the unconnected porosity of the condensed phase of nitrocellulose propellants on the linear burning rate with a pressure rise. A model based on experimental data is proposed for the variation in the linear burning rate taking into account the compaction of the fuel cells resulting in a nonlinear dependence of the burning rate on pressure. The temperature coefficient of the linear burning rate is found to exhibit a nontrivial behavior under pressure rise conditions in various ranges of initial temperatures. __________ Translated from Fizika Goreniya i Vzryva, Vol. 44, No. 5, pp. 58–63, September–October, 2008.     

Intrinsic reaction rate and the effects of operating conditions in dimethyl ether synthesis from methanol dehydration

The kinetic behavior of a commercial γ-Al₂O₃ catalyst for the methanol to dimethyl ether (DME) dehydration reaction has been investigated using a differential fixed bed reactor at the pressure range 1–16 barg within a temperature range of 260–380 °C. The experimental runs were performed in a wide range of feed to water ratios. The experiments were designed by general full factorial design (GEFD) and a novel rate equation has been developed which exhibited the best fitting with our experimental data. Based on the analysis of variance (ANOVA), the following order of importance for operating conditions was obtained when the objective function is the yield of DME: Temperature >Water % in feed >Pressure. In addition, the optimum operating conditions for the maximum yield of DME, were found at T= 380°C, P=16 barg and zero wt% of water in the feed.     

Pressure control in a semi-closed volume upon combustion of solid propellants with an exponent in the combustion law greater than unity

The problem of pressure control in a semi-closed volume by changing the critical cross-sectional area of a gas-release channel is considered upon solid-propellant combustion with the pressure, the combustion rate, and the free volume varied over a wide range (not smaller than one order of magnitude). For a system of automatic pressure control, a control algorithm is chosen and the conditions of partial parametric invariance with respect to the variable dynamic properties of the object to be controlled are formulated. The experimental results obtained upon improvement of the control system for solid rocket propellants whose exponent in the combustion law is greater than unity are given. The reasons for substantially nonstationary modes of operation of this system are considered, and a simplified model that approximates the phenomena of nonstationary combustion of a solid rocket propellant is proposed. The model is identified and the results of mathematical modeling are given. Recommendations on pressure control in the nonstationary modes of operation are given. Translated fromFizika Goreniya i Vzryva, Vol. 36, No. 5, pp. 45–56, September–October, 2000.     

Nanosized components of energetic systems: Structure,thermal behavior,and combustion

Ultrafine and nanosized powders of oxidizers and metals are considered as promising ingredients for the development of new highly effective solid rocket propellants. An ultrafine ammonium perchlorate (AP) powder and nanosized aluminum were produced by mechanical activation and investigated using electron and atomic force microscopy and X-ray powder and thermal analyses. It is shown that the activation energy of nanoaluminum oxidation is considerably lower than that for the micron-size powder, and the activation energy of the high-temperature decomposition for standard AP exceeds that for ultrafine AP. The exponent in the burning rate law decreases, and the burning rate increases by an order of magnitude if micron-sized aluminum is completely replaced by nanoaluminum in stoichiometric compositions containing ultrafine AP. __________ Translated from Fizika Goreniya i Vzryva, Vol. 43, No. 1, pp. 60–65, January–February, 2007.     

Structure of heterogeneous condensed mixtures

An analog method of random arrangement of solid spheres in space (solid disks in a plane) is proposed. The method consists of calculating the evolution of a system of spheres to an equilibrium state in which they do not intersect. This method was used to study the statistic structure of metallized compound solid propellants. Parametric investigation of various properties of solid propellants was performed over a wide range of aluminum particle sizes and component concentrations. It is shown that sinters whose dimensions depend linearly on the oxidizer particle size can form in combustion of the propellants. Special features leading to the formation of the sinters are studied. It is shown that at aluminum concentrations in the propellant higher than a certain critical concentration, combustion can yield a stable residue of sintered aluminum particles which is similar in shape to the solid propellant charge. Translated fromFizika Goreniya i Vzryva, Vol. 35, No. 5, pp. 65–74, September–October 1999.     

Emerging trends in advanced high energy materials

Enhanced performance of propellants and explosives is the most sought-after attribute for ambitious research programs in the field of high energy materials. Convergence of defence and space sector priorities has always kept research and development efforts in the area of propellants to the forefront. With the diminishing boundaries between rocket and gun propellants, as well as explosives, the possibility of low-vulnerable munitions with high performance potentials and spin-off advantages of research on rocket propellants are also emerging on the forefront. At the same time, an increasing predominance of missiles in today’s military warfare, as well as the space sector, has brought the issue of pollution by chlorine-containing combustion products of modern ammonium-perchlorate-based propellants into focus. A drastic transformation of high energy material technology is in offing. Research and development efforts made in this direction have brought an array of new materials into prominence. This paper reviews the recent work done in the frontier areas of advanced novel high energy materials. This paper covers the global scenario in the development of oxidizers, binders, plasticizers, high energy density materials, and insensitive high energy materials. __________ Translated from Fizika Goreniya i Vzryva, Vol. 43, No. 1, pp. 72–85, January–February, 2007.     

Experimental study of the thermophysical properties of carbon fibres

A number of thermophysical properties of carbon fibres was investigated. The measurement method, experimental setup, and experimental data obtained at 300–400 K are described. The temperature dependence of the thermal conductivity of carbon fibres is explained based on the phonon model of heat transfer. __________ Translated from Khimicheskie Volokna, No. 4, pp. 16–19, July–August, 2007.     

Temperature profile in the combustion wave of low calorific value propellants

Combustion wave temperature profiles are determined for two low calorific value propellants (Q _c = 2189 and 2518 kJ/kg). It is shown that the structure and parameters of the combustion wave differ significantly from those for previously studied propellants of medium (propellant N) and high (propellant NB) calorific values. At a relatively short distance from the burning surface, the temperature is significantly (180–270 K) higher than the calculated value due to fact the combustion products contain carbon black from the decomposition of heat-resistant dibutyl dinitrotoluene and dibutyl phthalate. Then, part of carbon black reacts endothermically with CO₂ and H₂O, leading to a decrease in temperature, which for the first sample is nevertheless 100–140 K higher than the thermodynamic value. For the investigated propellants, the activation energy of the leading reaction is the same as for the previously studied propellants, suggesting a common decomposition kinetics of the condensed phase regardless of the propellant composition. However, a uniform dependence of the burning rate on surface temperature is not observed. For low calorific value propellants, the surface temperatures are close to those for propellant N although their burning rate is significantly (2–2.2 times) lower. The causes of this fact are considered.     

A simplified mathematical modeling for thermo-catalytic decomposition of methane over carbon black catalyst in a fluidized bed reactor

A mathematical model for thermo-catalytic decomposition of methane over carbon black catalysts in a fluidized bed was proposed. The simplified isothermal, uniform flow model was considered and implemented into a computer code to predict the reactor performance. The experiment of methane decomposition into hydrogen and carbon was carried out in a fluidized bed of I.D of 0.055 m and height of 1.0 m. The range of reaction temperature was 850–900 °C, gas velocity was 1.0–3.0 U _mf , and catalyst loading was 50–200 g. The reaction parameters for model equation were determined from the curve fittings and the comparison of experimental data with simulation results showed good agreement for fluidized bed reactor system. From the simulation results, the fluidized bed performance with different operating conditions were obtained, and this simple model can be used to predict the performance of a larger scale fluidized bed reactor and also in determining the optimum operating conditions.